FIG. 1 shows a spring-grip dumb-bell according to the prior art which is comprised of two hand grips 11 joined by a spring member 12. This structure of spring-grip dumb-bell is specifically designed for developing the muscles of the hand. However, it can only be used to exercise one hand at a time. Furthermore, this structure of spring-grip dumb-bell cannot be adjusted to fit people of different ages because the spring force of the spring member is not adjustable. Therefore, old people usually use metal balls 13 to exercise the hand by holding the metal balls 13 in hand and then moving the fingers to turn the metal balls 13 against each other. However, because these metal balls are rounded and heavy, they are inconvenient to carry with oneself.
In order to eliminate the aforesaid drawbacks, the inventor invented a multi-functional handgrip and filed for a patent under application Ser. No. 08/254,901 which comprises a pair of U-shaped frames slidably engaged with each other through the inserts and connecting blocks disposed at both ends, wherein each connecting block is provided with a spring member, which gives a biasing force to the respective insert; a holding bar is disposed at the U-shaped frames for grasping. This structure of multi-functional handgrip is functional, however it still has drawbacks. One drawback of this structure of multi-functional handgrip is that the U-shaped frames are expensive to manufacture and complicated to assembled. Another drawback of this structure of multi-functional handgrip is that the holding bar and the spring members are securely fixed to the U-shaped frames and not replaceable. Therefore, the hardness of the holding bar cannot be changed to fit different requirements.